In Japanese Patent Application Laid-Open No. 2001-347953, in a steering apparatus of a tilt and/or telescopic scheme for a vehicle, an upper-side inner column is slidably fitted in a lower-side outer jacket fixed to the vehicle body. It is arranged such that the lower-side outer jacket and the upper-side inner column can be tilted together and the upper-side inner column can telescopically slide with respect to the lower-side outer jacket fixed to the vehicle body.
The lower-side outer jacket has a pair of clamp portions which are fixed to a part thereof at the rear side of the vehicle. At the time of tilt and/or telescopic clamping, these paired clamp portions are caused to approach each other so as to embrace the upper-side inner column to be fixed by clamping.
Further, since it is necessary to prevent the upper-side inner column from rotating with respect to the lower-side outer jacket fixed to the vehicle body, and also to provide a stopper for telescopic adjustment, a projection or a bolt formed on the lower-side outer jacket is engaged with an axial groove which is formed on the upper-side inner column in a part on a more frontal side of the vehicle than the clamp portions.
In Japanese Patent Application Laid-Open No. 6-219283, in a telescopic type steering apparatus for a vehicle, an upper surface having a substantially M shape of a distance bracket which has grooves extended in the axial diction for telescopic adjustment on both sides thereof is attached to a lower side of a steering column by welding. The steering column is arranged to be telescopically slidable, together with the distance bracket, with respect to a body-side bracket. At telescopic clamping, the steering column can be fixed by clamping a clamping bolt which is inserted through the grooves for telescopic adjustment of the distance bracket to thereby press the distance bracket on the body-side bracket with pressure.
Further, the distance bracket and the body-side bracket are in pressure contact with each other at flat surfaces thereof, so as to serve to prevent rotation of the steering column. At the same time, the clamping bolt is passed through the grooves for telescopic adjustment of the distance bracket so as to play the role of a stopper for a telescopic adjustment.
Also, in Japanese Patent Application Laid-Open No. 2000-118415, in a tilt-type steering apparatus for a vehicle, a distance bracket is attached to a steering column. The distance bracket is provided with a pair of flanges which are extended along the sides of the steering column and which are interposed between a pair of vehicle body side-brackets formed with grooves for tilt adjustment. The steering column is arranged to be tiltable with respect to the body-side brackets, together with the distance bracket. At tilt clamping, it is arranged such that the steering column can be fixed by clamping a clamping bolt which is inserted through the grooves for tilt adjustment of the body-side brackets to thereby press the distance bracket on the body-side bracket with pressure.
Generally, in case of a steering column in which a distance between a steering wheel and a steering gear mechanism is short or a steering column in which a collision stroke has to be set at great, it is difficult to securely obtain both a stroke for telescopic adjustment and the collision stroke, in order to establish a telescopic adjustment structure.
To cope with a request for maintaining the steering column with a high rigidity, as disclosed in Japanese Patent Application Laid-Open No. 2001-347953, such a structure is effective as that an inner column is clamped by a pair of clamp portions, which requires high precision of the outer periphery of the inner column and of the inner diameter of an outer jacket in order to avoid very small backlash in case with a high rigidity (particularly with high oscillation rigidity), but can be processed comparatively easily because of a circular section thereof.
However, in the structure disclosed in Japanese Patent Application Laid-Open No. 2001-347953, it is required to separately provide a structure for preventing rotation of the inner column at a position different from that of the clamp portion.
Also, in case of a short steering column, it is difficult to secure a position at which the structure for preventing rotation of the inner column is provided. It can be considered that an axial groove is formed on the inner column side in the clamp portion to cope with this problem. However, the formation of the axial groove of the inner column may result in that the inner column is easily flexed at clamping to thereby deteriorate the retaining rigidity.
Further, when an axial groove is plastically processed on an inner column in the form of a thin pipe as a deformed cross-section thereof, it is difficult to secure a dimensional accuracy, which may results in problems such as a defective telescopic operation or backlash sensed in operation. Further, when a plate for preventing rotation is fixed by welding, the inner column may be deformed by welding to bring about telescopical defective operation.
Further, in Japanese Patent Application Laid-Open No. 2001-347953, axial slits are provided on the outer jacket at portions at which the pair of clamp portions are formed. However, no other slit is provided on the outer jacket which is therefore formed cylindrical except the above portions. The other part is formed to be cylindrical. Since the outer jacket and the inner column are telescopically slidable, a gap is inevitably required therebetween. Further, since the steering shaft has to slid telescopically, a gap is required also inside the outer jacket. As a result, backlash feeling may be caused in steering, and the retaining force of the outer jacket may be deteriorated.
Further, as disclosed in Japanese Patent Application Laid-Open No. 6-219283, in the telescopic structure in which an upper side of the distance bracket is attached to a lower side of the steering column by welding, moments are generated on a body attaching surface, the clamp portions and the center of the inner column (the center of the steering wheel), respectively, which is disadvantageous in terms of the rigidity.
Further, a structure as disclosed in Japanese Patent Application Laid-Open No. 2000-118415 in which a pair of flanges of the distance bracket extended along the sides of the steering column are interposed between a pair of vehicle body side brackets, is effective in terms of the rigidity. However, in such a structure, if it is arranged to be telescopic type, the number of the constituent parts may be increased.